1. Royal Manticoran Navy (RMN)

The normal uniform is "Black and Gold"
(primarily black, though. There is little reference to which
bits are gold)(Assumably just highlights).

The Captain wears a white beret, all other crew wear a black beret.
The beret has a badge showing the Manticoran coat of arms on it.

There is a tunic (primarily black) (NO buttons) with epaulets, and a
turtleneck white blouse worn underneath. Trousers are black, with a gold
stripe along the outer seams (This may be the dress uniform only)

Previous hyper-capable commands are indicated by a series of gold stars
embroidered on the breast of the tunic (left?)

There is a Shoulder Flash on the right shoulder of the tunic, showing a
rampant manticore in black on a red background.

On the left shoulder is a horseshoe shaped patch with the ships name on
it.

Assumably there are also unit/speciality patches as well, but they are
not mentioned specifically in the books.

The full Mess Dress uniform includes a ceremonial sword, and there is
mention of considerable amounts of braid (for senior ranks)

Known Rank insignia:

Ensign

1 gold band on sleeve

Lt-Jg

1 1/2 gold bands on sleeve

Lt

2 gold bands on sleeve

Lt-Cmdr

2 1/2 Gold bands on sleeve

Commander#

Three Gold Bands on Sleeve

Captain JG#

Four Gold Bands on sleeve,
4 "pips" on collar

Captain of the List#

Four Gold Bands on sleeve,
single "planet" on
collar

Commodore#

Broad band, 3 normal bands,
2 x "planets" on collar

Rear Admiral

2 Broad bands, 2 normal,
1 x 9-pointed star

Vice Admiral

3 Broad bands, 1 normal,
2 x 9-pointed stars

Admiral#

Four broad gold Bands on sleeve,
3 x 9-pointed stars on collar

(The '#' are confirmed by actual book references, the others are
inferred)

This is the sum total of my knowledge from scouring through the books.

The rank insignia seem to be more or less in line with the current US
Navy rank insignia, although there does not appear the be an equivalent
of "Captain (Junior Grade)" in either the US or British navies.

That being the case, the following collar insignia could apply:

Collar Insignia

Ensign

1 'closed' pip

Lt. JG

1 'closed' pip and 1 open 'pip'

Lt. SG

2 'closed' pips

Lt. Cmdr.

2 'closed' pips and 1 open
'pip'

Cmdr.

3 'closed' pips

Capt. JG

4 'closed' pips

Capt. SG

Full planet

Commodore

2 planets

Rear Admiral

1 star (nine pointed)

Vice Admiral

2 stars (nine pointed)

Admiral

3 stars (nine pointed)

Fleet Admiral

4 stars (nine pointed)

COMMENT:There should be something to indicate if
an admiral is "of the Red" or "of the Green".
// Bo Johansson

(A 'closed' pip is a solid shape, and an 'open' pip is a hollow shape)

As for noncoms, nothing specific is mentioned in the books but:

"US Army uses long diagonal stripes on left fore-arm for enlistments,
short horizontal bars for combat tours (hershey bars)."

"Officers wear enlistment stripes only if earned for service prior to
receiving a commission."

2-7. Other Services:

Manticoran Marines wear green and black

Grayson Navy wears blue.

"...The short waisted tunic was a lighter blue than the trousers,
which seemed an equally unnatural reversal of the way things ought to be,
and the gold leaves on her visor...."
"...high peaked, visored cap..." (from Flag in Exile)
(and mentions archaic buttons)

Grayson Marines wear green and brown

Masadan Navy wears Scarlet and Gold

IAN (Anderman Navy) wears white.

I THINK that the PN has a uniform similar to the RMN, but there is no
actual mention I can find for sure.